The subject invention relates to a universal production ball grid array socket for establishing solderless connections between the conductive balls of a ball grid array package and a printed circuit board. More particularly, the lead balls of a ball grid array package can be solderlessly mounted within the contacts of the ball grid array socket.
There currently exists several different methods for packaging semi-conductor devices. One popular type of semi-conductor packaging is referred to as a quad flat pack (QFP), which is a type of peripheral lead package. A new type of packaging technology is referred to as the ball grid array (BGA). The ball grid array was introduced by International Business Machines Corp. (IBM) and includes a number of benefits, including small package size, good yield, better electrical performance, and lower profiles, among others.
The BGAs generally place conductive ball leads over the entire surface of a chip, instead of just around the edges. Thus, BGA packages allow system designers to place more leads in a given package size using looser tolerances than peripheral lead type packages such as the quad flat pack. Therefore, board producers are not required to use the fine pitch spacings that are now necessary for high lead count packages. Also, BGAs have finer pitch spacings than pin grid arrays (PGA), since the solder balls do not have the coplanarality problem associated with through-hole PGAs. In the prior art, the electrical connection between the BGA package and underlying PC board was generally provided by soldering the ball leads which are located underneath the BGA package onto pads which are provided on the upper surface of printed circuit boards.
In many applications the soldering of the ball leads of the ball grid array package to the printed circuit board is undesirable. For example, it is impossible to visually locate a short or ground between the ball grid array package and printed circuit board. Usually, an expensive X-ray technique is required to inspect the connections since the ball leads are hidden under the ball grid array package. Further, the increasing number of ball leads being provided by ball grid array packages makes the soldering of the ball grid array packages to printed circuit boards more difficult.
Accordingly, in the prior art, an improved connector has been developed which is designed to eliminate the need for the soldering the ball leads of a BGA package to a printed circuit board. One example of a device which satisfied this criteria is the fuzz ball socket. The fuzz ball socket comprises a plurality of electrical contacts mounted within an insulated housing. Each contact resembles a brillo pad, made up of individual gold plated wires, forced into a through hole of the insulated housing. Using a great deal of pressure the fuzz ball socket can be forced down and bolted onto a PC board, thereby providing the proper electrical contact. The BGA package is then placed in the fuzz ball socket, a metal cover is placed on top of the BGA package and a great deal of pressure is exerted on the cover to force the ball leads of the BGA package into the proper electrical connection with the fuzz ball socket.
In many applications, the necessity of using a great deal of pressure to force the ball leads of a BGA package into a fuzz ball socket is undesirable. For example, the number of ball leads placed on a BGA package are increasing, thereby making the mounting of a BGA package within a fuzz ball socket increasingly difficult since greater and greater pressure is required to create a proper electrical connection. Further, the great force required to push the ball leads into contact with the fuzz ball socket creates wear on the BGA ball leads and increases the likelihood of distorting the ball leads. Additionally, the manufacture of a fuzz ball is very expensive since wire must be individually wired into each through hole.
BGA packages are often provided with eutetic solder ball leads comprising 63/37 tin/lead solder. Unfortunately, 63/37 tin/lead solder is a relatively soft material which is readily distortable. Most solderless connections, as with the aforementioned fuzz ball socket, rely on spring forces to maintain electrical connections. The application of the spring forces to the solder ball leads may cause distortion thereof.
It is therefore an object of the subject invention to provide a universal production ball grid array socket which eliminates the necessity to solder the conductive ball leads of a BGA package to the contacts of a printed circuit board.
It is another object of the subject invention to provide a universal production ball grid array socket which reduces the large amount of pressure required to mount a BGA package onto a BGA socket.
It is still another object of the subject invention to provide a universal production ball grid array socket having a unique resilient electrical contact capable of achieving electrical connection between the contact of a circuit board and the conductive ball lead of a BGA package. In particular, a socket is disclosed having a contact which resiliently expands to electrically engage conductive ball leads of varying diameters.
It is a further object of the subject invention to provide a universal ball grid array socket wherein the ball grid array package is positively locked within the housing of the ball grid array socket thereby preventing the degradation of the electrical connection due to vibration or other disturbance.
It is an object of the second embodiment of the subject invention to provide a coverless universal ball grid array socket having resilient contacts for clasping the ball leads of a BGA package thereby establishing a relatively high retentive force and preventing the degradation of electrical connection due to vibration or other disturbance.
It is an object of the third embodiment of the subject invention to provide a coverless universal ball grid array socket having resilient contacts for clamping the ball leads of the ball grid array package where only a slight portion of the resilient contact is utilized as a means for preventing contact slippage within the universal ball grid array socket.
It is an object of the fourth embodiment of the subject invention to provide a coverless translucent ball grid array socket which allows for quick and easy inspection of a ball grid array package and ball grid array socket combination.
An additional object of the subject invention is to provide a method for mounting ball leads onto a ball grid array socket.
It is yet another object of the subject invention to provide a transition adaptor for converting an unsocketable integrated circuit into a socketable integrated circuit.